Referring to FIG. 1, a typical loudspeaker driver includes a cone-shaped diaphragm 1 that is movably suspended (using a surround 6 or the like) in a basket 2 for motion along central axis thereof, and a single motor 3 mounted on the basket that includes a voice coil 4 having a central axis 5 in substantial alignment with the central axis of diaphragm 1, which is coupled directly to the back of diaphragm 1 in order to move the diaphragm axially in response to an AC signal.
It is well known that as the size of the diaphragm increases and/or when more power is desired the size of the magnet required for driving the voice coil increases. Also, as the size of the diaphragm increases the size of the basket is increased, which in turn increases the profile (i.e. the front to back thickness) of the driver. Thus, woofers (drivers used for reproducing sound in the bass range, e.g. 20 Hz to 3000 Hz), which typically include larger diaphragms (compared to tweeters), require large motors and typically have larger profiles.
The profile of the driver directly affects the size of the speaker cabinet that receives the driver. A speaker cabinet that receives a woofer, therefore, requires a relatively large cabinet having a relatively large profile (i.e. front to back thickness).